f(sinx)=1-cos2x =1-（1-2（sinx）²）=2（sinx）²求 f（x）=2x²f(cosx)=2（cosx）²f(x+1/x)=x²+1/x²=x²+1/x²+2-2=（x+1/x）²-2f（x）=x²-2f(x-1/x)=（x-1/x）²-2=x²+1/x²-4
